ARCHAR, Bulgaria — On the banks of the Danube, in the northwest corner of Bulgaria, lie the remnants of an ancient Roman settlement called Ratiaria, host to a priceless cultural heritage. Craters pockmark the huge site, evidence of a scourge threatening one of the world's great troves of antiquities: looters digging for ancient treasure to sell on the black market.

Archaeologist Krasmira Luka, who heads a team excavating part of the 80 hectare (200 acre) site, says the area has been repeatedly raided by thieves who dig pits looking for ancient coins and jewelry. Everything else, including precious ceramic vessels and other historically significant artifacts, is smashed to pieces.

"Destroying the items is not just a crime, it's an irreparable tragedy," Luka said, looking out at a moonscape littered with shards of ceramics or glassware destroyed by the diggers. "The day after our team leaves the site, the diggers are in place. It's an uneven battle."

Located on the crossroads of many ancient civilizations, Bulgaria is ranked by its scholars as behind only Italy and Greece in Europe for the numbers of antiquities lying in its soil. But Bulgaria has been powerless to prevent the rape of its ancient sites, depriving the world of part of its cultural legacy and also costing this impoverished Balkan nation much-needed tourism revenue.

Police reports indicate that every day up to 50,000 people are engaged in treasure hunting raids across Bulgaria, a country of 7.3 million. According to Angel Papalezov, a senior police officer, hundreds of thousands of artifacts are smuggled out of the country every year, with dealers hauling in up to $40 million.

But Ratiaria is the most drastic example of the looting that has been going on over the last 20 years, since the fall of communism. The first excavations here were carried out by Bulgarian archaeologists between 1958 and 1962. They were renewed in 1976 by an Italian team, but lack of funding forced them to leave the site in 1991.

Western experts call Ratiaria a world-class archaeological site that is under grave threat.

"Ratiaria has a great archaeological and historical significance not just of regional and national importance to Bulgaria but internationally for the study of the Roman Empire," said Jamie Burrows, an archaeologist at the Nottingham University, who has spent several years working at Ratiaria.

"Such a site could have been North West Bulgaria's 'Pompeii', bringing wealth to a poor region in need of such tourism," he said in an email to The Associated Press. "Without quick efficient action this opportunity may sadly be missed."

Ancient sites were protected during communist times by a strong fear of the omnipresent police and harsh punishments for any law-breaking activity. Since the collapse of the totalitarian system, many have taken up looting to earn a living. Organized by local mafia, looting squads that have mushroomed all over the country are well equipped with metal detectors, bulldozers, tractors and even decommissioned army vehicles.

Bulgaria hosts some of the most unique and vulnerable cultural resources in Europe.

In addition to the numerous Neolithic, Chalcolithic and Bronze Age settlement mounds, there are significant remains of Hellenistic, Roman and Byzantine urban centers. Perhaps most notable among Bulgarian antiquities are the remains of the Thracians, a powerful warrior kingdom conquered only by Alexander the Great and the Roman Empire. The best known Thracian remains in Bulgaria are tombs and burial mounds which contain stunning gold and silver work.

In early October, some 5,000 Roman items were handed over to the National History Museum in Sofia. They were seized at a border crossing with Serbia, just few miles (kilometers) west of Ratiaria.

Presenting the collection, museum director Bozhidar Dimitrov said that he was glad to have the lost treasure back — but also saddened because it was proof of how widespread illegal treasure hunting was in Bulgaria.

Through the broken windows of a deserted house on the Ratiaria site, there are pits up to three meters deep dug by looters under the floor.

"It was bought by looters who have used it as a shelter where they can dig without being bothered by police," Luka said. If they get caught, they usually claim they are on their way to hand over the find to the museum.

Coins and other treasures found by looters are sold to people who smuggle them abroad. Roman items from Ratiaria can be found in auction houses and antiquity collections around the world. For the looters in a part of Bulgaria declared by Eurostat, the EU's statistical agency, as "the European Union's poorest region," the site represents an almost irresistible temptation.

Luka told the story of three men from the nearby village or Archar, who had found a golden coin and sold it to smugglers for 1,500 euro, which equals the amount of four monthly average salaries in Bulgaria. "Months later the same coin was sold in Germany at a price many times higher," Luka said.

"But it is not only the looters with the shovels who are responsible," Luka said, "there are a lot of people up the chain, and they enjoy the highest protection." Over the last two decades, she said, organized crime groups have constantly bribed police officers, prosecutors and local officials who have sheltered their illegal activities. Those who usually get caught and sentenced, however, are from the lowest level of the well-organized scheme.

With more than 50 percent of the 2,700 inhabitants of Archar jobless, Mayor Emil Georgiev seems unable to stop the daily attacks of looters seeking the treasure that is supposed to change their life.

"Usually they work late at night or at weekends or holidays," the mayor said, adding that some 20 villagers have been convicted over the last year and ordered to serve different terms of probation by performing community service.

"Recently we received government funds that guarantee jobs for just eight people who will work as guards at the archaeological site," Georgiev said, raising his shoulders when asked how such a small group can protect the huge area.

In Vidin, the main city of the region, the newly appointed district governor Tsvetan Asenov said that preserving the archaeological site and opening it up for tourists was one of his priorities, but complained that this was not easy in a time of acute economic crisis.

Experts say they have no way to gauge the extent of the pillaging.

"There are hundreds of tombstones and statues in local museums, but what we don't know exactly is how many more such relics were smuggled out of the country and are now in Italy, Munich or Vienna," said Rumen Ivanov, Roman History professor at the National Institute of Archaeology.